At low engine speeds, a locomotive engine does not need to have fuel delivered to all the cylinders to operate. However, in conventional systems, the fuel is continuously delivered to all the cylinders irrespective of engine speed, and this in turn means unnecessary fuel is being wasted, and in turn unnecessary emissions are being generated.
It is known to selectively cut off fuel delivery to a select amount of engine cylinders (called “skipfire” because firing of these cylinders is skipped over), leaving enough cylinders operating to maintain engine speed. This in turn reduces fuel consumption and emissions. Once engine speed picks back up above a predetermined threshold, the system will return to normal operation and enable fuel delivery to all engine cylinders for delivering full power.
Known skipfiring systems are provided in electronic fuel injected engines in which a controller electronically and individually controls the injectors. Examples of such skipfiring systems are disclosed in U.S. Pat. Nos. 5,826,563; 6,286,488; and 6,405,705.
However, known engines also feature mechanical control of fuel injectors as distinguished from electronic control. That is, the engines include rocker arm assemblies that cooperate with the camshaft of the engine to mechanically actuate the fuel injectors.
One aspect of the present invention is to provide a skipfire control system for use with locomotive engines using mechanically controlled fuel injectors.
In accordance with the principles of the present invention, this aspect may be achieved by providing a skipfire control system for use in a locomotive engine including a plurality of fuel injected cylinders, each of the plurality of cylinders having a fuel injector and an injector rocker arm movable to actuate the fuel injector to inject fuel to the associated cylinder. The engine also includes a camshaft engagable with each of the injector rocker arms to move the rocker arms for actuation of the fuel injectors. The skipfire control system comprises a plurality of skipfire mechanisms, each of the plurality of skipfire mechanisms being operatively associated with a respective injector rocker arm of the plurality of cylinders. Each of the plurality of skipfire mechanisms includes an actuator movable between (1) an inoperative position wherein the actuator allows the camshaft to engage and move the associated injector rocker arm to actuate the associated fuel injector, and (2) an operative position wherein the actuator disengages the associated injector rocker arm from the camshaft to prevent the associated rocker arm from being moved by the camshaft to actuate the associated fuel injector. A skipfire controller is operatively connected to the plurality of skipfire mechanisms. The skipfire controller is responsive to an engine operating parameter to actuate selected ones of the plurality of skipfire mechanisms so as to move the actuators thereof to the operative positions to thereby prevent actuation of the fuel injectors associated with the selected ones of the plurality of skipfire mechanisms.
Another aspect of the invention relates to a locomotive comprising an engine including a plurality of fuel injected cylinders, each cylinder having a fuel injector and an injector rocker arm movable to actuate the fuel injector to inject fuel to the associated cylinder. The engine also includes a camshaft engagable with each of the injector rocker arms to move the rocker arms for actuation of the fuel injectors. The locomotive also includes a skipfire control system comprising a plurality of skipfire mechanisms. Each of the plurality of skipfire mechanisms is operatively associated with a respective injector rocker arm of the plurality of cylinders. Each of the plurality of skipfire mechanisms includes an actuator movable between (1) an inoperative position wherein the actuator allows the camshaft to engage and move the associated injector rocker arm to actuate the associated fuel injector, and (2) an operative position wherein the actuator disengages the associated injector rocker arm from the camshaft to prevent the associated rocker arm from being moved by the camshaft to actuate the associated fuel injector. A skipfire controller is operatively connected to the plurality of skipfire mechanisms. The skipfire controller is responsive to an engine operating parameter to actuate selected ones of the plurality of skipfire mechanisms so as to move the actuators thereof to the operative positions to thereby prevent actuation of the fuel injectors associated with the selected ones of the plurality of skipfire mechanisms.
Still another aspect of the invention relates to a method of skipfiring a locomotive diesel engine including a plurality of fuel injected cylinders, each of the plurality of cylinders having a fuel injector and an injector rocker arm movable to actuate the fuel injector to inject fuel to the associated cylinder. The engine also includes a camshaft engagable with each of the injector rocker arms to move the rocker arms for actuation of the fuel injectors. The method comprises providing a plurality of skipfire mechanisms, each of the plurality of skipfire mechanisms operatively associated with a respective injector rocker arm of the plurality of cylinders. Each of the plurality of skipfire mechanisms includes an actuator movable between (1) an inoperative position wherein the actuator allows the camshaft to engage and move the associated injector rocker arm to actuate the associated fuel injector, and (2) an operative position wherein the actuator disengages the associated injector rocker arm from the camshaft to prevent the associated rocker arm from being moved by the camshaft to actuate the associated fuel injector. The method also comprises monitoring an engine operating parameter, and actuating selected ones of the plurality of skipfire mechanisms responsive to the engine operating parameter so as to move the actuators thereof to the operative positions to thereby prevent actuation of the fuel injectors associated with the selected ones of the plurality of skipfire mechanisms.
These and other aspects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, the principles of this invention.